I have an marineland eclipse 3 aquarium that has a bio wheel and the instructions say to change the filter every 3-4 weeks. I've read on this forum and other places that I shouldn't ever change a filter but instead just rinse it out when it looks too dirty. I'm just wondering if this is true for me since I have the bio wheel. And also I just bought a 2nd tank that is a marineland crescent 3 with a bio bag instead of a bio wheel, so the filter and bio bag are all one piece. So should I not change this filter at all either?

Instruction on the package tell you to change the filter media for two reasons, to make money and if it also contains activated charcoal it need to be changed due to it being used up.

Most carbon is of low grade and needs to be changed at least every 3-4 week.

I don't use carbon in my tanks, I don't need it and as long as you are making the needed water changes IMO/E you don't need carbon.

Activated charcoal or often called carbon will remove tannin from the water, remove smells, remove medications, help make the water look more clear...but so will a water change......

I make my own filter media from the poly fill I get from the craft department and I change it out when it is falling apart maybe 1-2 times a year.
I give it a swish/rinse in old tank water 1-2 times a month or if the water flow slows on the filter. This keep the good bacteria alive, untreated tap water will kill the good bacteria. You want the filter media to look dirty, all you do with the swish in old tank water is to remove the big pieces of gunk.

On my HBO filters that have the plastic with blue filter media and carbon in the middle, I cut a slit in the media and dump the carbon and save for later and stuff the inside with the polyfill, soon they do fall apart so I save the black plastic part and use twine and wrap around the pollyfill to keep it attached to the plastic part.

When you do change the filter media, remove part of the old filter media and keep it in the filter for a week or two until the new filter media has time to seed with the good bacteria.

Bio wheel should never need to be changed, a good swish in old tank water with a water change if they stop turning or have big pieces of gunk on them it all that is needed to be done.

The Bio-ball, need a rinse in old tank water 3-4 times a year to keep the oxygenated water flow though them to keep the good bacteria thriving.

Its up to the hobbyist which method you want to go with, but for me I want to keep my money in my pocket and find other methods that work as well.

Thanks! :) Yeah, the filter has charcoal, so that must by why it recommends the changes. I was wondering if they just wanted my money hehe. I knew that the bio wheel never should be changed, I just wondered if since the wheel should have the bacteria growing on it, that meant the filter sponge won't have many bacteria.

I can't remember right now if the new tank with the bio bag also has charcoal, I'll have to check. I just started trying a fishless cycle last night, I hope it goes well. I'm going to get a male betta fish, my daughter has a female in her tank.

I have Marineland Bio-Wheel filters and while I do prefer the carbon, in reality I seldom change them. At some point the carbon will reach its limit to adsorb gunk, and become neutralized. As long as you rinse the filter as OFL recomends, you could use the filter until it literally starts to fall apart.

If I see the water start to get cloudy or discolored, then I'll toss in a new one. Otherwise I leave them alone and simply rinse them in the bucket of old tank water when I do a water change.

I have a couple of eclipse 3s, and I do something similar to OFL. I cut the filter floss down the side to expose all the carbon beds and pour out the used carbon, then I fill the beds up with new Matrix Carbon (a decent brand), and shove some 50 micron filter floss in over it so the carbon doesn't fall out. Give it a quick rinse, and then put the cartridge back in. :) Polyfill would probably be cheaper than the 50 micron, but 50 micron also makes for a really good algae scrubber, hahaha. Replacing the carbon is not totally necessary since you will probably be doing the same amount of water changes either way--it's up to you if you want to have to change out the carbon. I like that having the carbon there because that along with lots of live plants gives me some extra leeway if some emergency happens and I just have to push a water change back a day.